Issue 3
JTAM, Sofia, vol. 18 Issue 3 (1987)

Object and Methods of Technical Diagnosis

G. Meltzer
Academy of Sciences of DDR, Inst. Mech.


The general approach to technical diagnostics is set forth. Realization methods are described. A mathematical description of time varying systems and diagnostic models of mechanical systems are given. Diagnostics is based on experimental data by means of a parametric model. Some diagnostic symptoms are presented. Information about investigations in the domain is given and it concerns the Institute of Mechanics with the Academy of Sciences of DDR.

JTAM, Sofia, vol. 18 Issue 3 pp. 011-020 (1987), [Full Article]

Adjustment of Feedback Gains in Nonsingular Position Control Systems of Manipulators

P. Ðœarinov, P. Kiriazov
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8

A direct method is proposed to adjust the feedback gains in “point-to-point" control. The method is based on manipulator real dynamics. The control synthesis algorithm consists in an iterative adjustment of the feedback gains to proportional derivative controllers of the joint actuators. Control laws are in agreement with minimum energy loss criteria due to continuous magnitude control functions. The values of the feedback gains have been derived from the exact solution of the corresponding two-point boundary value problem. The method can be applied to the manipulator itself for final adjustment of the control parameters. A dynamic model of a direct current driven manipulator with cylindrical coordinates is taken into consideration as a demonstrative example.

JTAM, Sofia, vol. 18 Issue 3 pp. 021-024 (1987), [Full Article]

Dynamics of a Manipulation Robot with Elastic Links in Case of Single Zero Root of the Characteristic Equation

S. Butchvarov1, P. Kolev2
1High. Inst. Mech. Electr. Eng., Sofia
2High Military Sch. of Civ. Eng. "Gen. B. Ivanov", Sofia

The paper presents dynamic examination of PPP-structure robot when one of its regional motions is caused by the force Fд = L – Vq1–Wq1. The robot represents a two mass elastic system with two degrees of freedom by assumption. The differential equations of motion have been derived. An analytic solution of the perturbed motion has been constructed in asymptotic series by means of Bogoljubov-Mitropolski method. The regime characteristic influence on system oscillation has been analysed.

JTAM, Sofia, vol. 18 Issue 3 pp. 025-029 (1987)
Stochastic Evaluation of Industrial Robot Accuracy Characteristics by a Computing Procedure

B. Bekjarov, A. Farhi
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8

A mechano-mathematical accuracy model of tree-like structure mechanical systems is used to propose stochastic evaluation criteria for industrial robot positioning errors and estimation algorithms. A computing procedure has been developed to evaluate industrial robot accuracy characteristics stochastically. The computing procedure itself is intended to work in a dialogic regime and in IBM-PC/XT personal microcomputers.

JTAM, Sofia, vol. 18 Issue 3 pp. 030-035 (1987)
Hydrodynamic Interaction between Two Flattened out Spheroids in Uniform Viscous Flow with Moderate Reynolds Numbers

Tzv. Kotzev, Z. Zapryanov
Inst. Mech. Biomech., Bulg. Acad. Sci. Bl. 8

The paper is devoted to numerical examination of hydrodynamic interaction between two flattened out spheroids when the flow past stream is parallel to the centre straight line. The spheroid surfaces are not coordinate ones in any coordinate system. Thus, the method of numerical matching the solutions round the two bodies has been applied to solve the corresponding boundary value problem for the complete Navier-Stokes stationary equations. What is examined are the viscous flow vortices behind the bodies, the drag forces which depend on the distance between the bodies, the eccentricity and the Reynolds number. The well-known solution of a single spheroid flow past has been derived in the particular case of great distance between the spheroids. Many figures illustrate the dependences that have been obtained.

JTAM, Sofia, vol. 18 Issue 3 pp. 036-043 (1987)
Linear Instability of a Nonviscous Two-Layered Capillary Jet

O. Kamenov, S. Radev
Inst. Mech. Biomech., Bulg. Acad. Sci., Bl. 8

What is examined in relation to time increasing two-dimensional perturbations is the linear instability of a nonviscous two-layered jet that flows in an ideal gas. Two families of time increasing pulsations have been presented. The pulsations develop at basic flow velocity when the kernel fluids and the concentric layer are of different density in the general case. The increment asymptotic behaviour has been considered under small values of the surface-tension nondimensional coefficients and thin concentric layer. Some results of numerical experiments are presented and they characterize the increase coefficient dependence on the wave number. The kernel length and the concentric layer in two-layered jet have been determined in case of fluid density variation.

JTAM, Sofia, vol. 18 Issue 3 pp. 044-053 (1987)
Photo-Absorptive Thermocapillary Convection in Viscous Liquid Thin Layer. I. Light Field

S. Slavchev
Inst. Mech. Biomech.. Bulg. Acad. Sci., Bl. 8

The problem of photo-absorptive thermocapillary convection in viscous semi-transparent liquid thin layer has been formulated in the paper. The liquid motion is caused by irregular temperature distribution within the volume and over the free surface due to radiation energy partial absorption and heat transformation. What is determined on the grounds of the geometric optics method is the light field in case of an arbitrary distribution of the falling wave illuminating.

JTAM, Sofia, vol. 18 Issue 3 pp. 054-062 (1987)
Some Mechanical Quantity Dependences within the Coat-Saddle Boundary

H. Koujoumdjiev
High Techn. Sch. "A. Kanchev", Rousse

General mechanical quantity dependences have been derived. They refer to stressed elastic coating and elastic saddle in the neighbourhood of a point from the connective plane. It is possible to verify approximate solution results applying the dependences.

JTAM, Sofia, vol. 18 Issue 3 pp. 063-069 (1987)
Stressed-Strained State Experimental Examination of a Rectangular Base Sloping Shell in Case of Positive Gauss Curvature and Durable Loading

Chong Min Bin, I. Marchokov
High. Inst. Arch. Civ. Eng., 2 Hr. Smirnenski Blvd., Sofia

Rectangular base sloping shells with positive Gauss curvature are notable for economical expenditure of concrete-steel materials. Their application to civil engineering practice extends in Viet-Nam. Some recommendations and conclusions to design and realization improvement of such reinforced cement shells are listed in the paper using long-term experimental examination.

JTAM, Sofia, vol. 18 Issue 3 pp. 070-075 (1987)
Multi-Layer Cylinder Subjectedto Internal Loading

A. Baltov1, St. Vodenicharov1, I. Nikolova1, G. Kortenski2, M. Marinov2
1Inst. of Mech. and Biomech., Bulg. Acad. Sci., Bl. 8
2Inst. Met. Res. Techn., Bulg. Acad. Sci., Bl. 1

Stressed-strained state determination method is presented in the paper. The method is applied to a multi-layer cylinder that has been subjected to internal dynamic loading. The cylinder itself is considered to be made of substitutive homogeneous material which reflects energy dissipation identically due to layer passage. The wave propagation problem of the substitutive material cylinder is solved following the correspondence principle.

JTAM, Sofia, vol. 18 Issue 3 pp. 076-079 (1987), [Full Article]

Reflection and Refraction of Waves of Discontinuities in Nonlinear Elasticity

Ts. Ivanov
Inst. Mech. Biomech., Bulg. Acad. Sci., B1. 8

The paper considers reflection and refraction of waves of discontinuities which fall normally from a plane that is perpendicular to the propagation direction. Coefficient formulae of reflection and refraction have been derived in case of nonlinear elasticity. The results are analogous to harmonic wave reflection and refraction in the particular case of linear elasticity.

JTAM, Sofia, vol. 18 Issue 3 pp. 080-084 (1987)
Examination of High Tempera ture Creep and Durable Strength of Light Drill Pipe Material

V. Gorbatenko
Kuybishevski Polytechnical Inst., USSR

What is examined is the creep and the durable strength of aluminium based light alloy materials that have been used in drill pipe production. The advantage of D16T alloy is shown in deep drilling with characteristic temperature and tension rises which are about the durable strength limit. Experiments corroborate the necessity to give an account of scale factor part in calculating the drill pipe stressed-strained state.

JTAM, Sofia, vol. 18 Issue 3 pp. 085-090 (1987)